There is a current need for an airborne vehicle capable of performing surveillance, reconnaissance, communications, weapons delivery, or other missions, which can remain aloft for long periods of time. Because HTAs require propulsion to stay aloft, their endurance is limited by their fuel capacity and payload. The High Altitude Long Endurance (HALE) aircraft community has focused considerable effort over the past twenty years on designs to extend vehicle endurance up to one or two days, with future advanced concept designs targeting four to five days. However, airborne Intelligence, Surveillance, and Reconnaissance (ISR) mission requirements have lasted much longer than four to five days, as evidenced in recent theatres of conflict and other applications. Additionally, other missions such as communications relay, electronic warfare, and weapons delivery may also involve extended duration mission requirements. Furthermore, operational costs of carrying out these missions vary inversely as a function of aircraft endurance.
On the other hand, LTAs often have adequate endurance and ample payload capacity but lack the propulsion and energy means required to keep a large LTA in one location, given the winds at high altitude. Additionally, LTAs are limited by materials technology. For example, ultraviolet radiation causes degradation at high altitude over periods of time. LTAs are further limited by operational constraints on takeoff and landing as well as survivability in military environments.